1. Technical Field of the Invention
The present invention relates to a curable thermosetting resin composition having enhanced fracture toughness as a result of the incorporation of reactive thermoplastic oligomers therein. More specifically, the present invention relates to a composition comprising a thermoset resin which contains fluorine and containing at least one fluorine containing thermoplastic homopolymer component which is soluble in the thermoset. Said thermoplastic polymer undergoes an in-situ phase separation process during cure to form a microphase separated multiphase thermoset material.
Furthermore, the present invention relates to a composition comprising a thermoset resin which optionally contains (i.e., it may or may not contain) fluorine, bromine or both and containing at least one thermoplastic co-, ter- or multicomponent polymer component which is fluorine-containing and is soluble in the thermoset. Said thermoplastic polymer undergoes an in-situ phase separation process during cure to form a microphase-separated multiphase thermoset material.
Furthermore, this invention relates to a composition comprising a thermoset resin which may or may not contain fluorine, bromine or both and containing at least one bromine-containing homo- or multicomponent thermoplastic polymer modifier optionally containing a different halogen which is soluble in the thermoset. Said thermoplastic polymer undergoes an in-situ phase separation process during cure to form a microphase-separated multiphase thermoset material.
The resin composition may be impregnated into various types of reinforcement, yielding insulating materials with either a controlled coefficient of thermal expansion (CTE) or a low dielectric constant or both.
Furthermore, this invention relates to a curable material useful in conducting heat or electricity comprising a thermosetting material and inorganic or metal particles which exhibit high thermal stability with controlled CTE.
Furthermore, the present invention relates to a curable material useful in the fabrication of prepreg layers for use in the manufacture of articles related to electronic packaging structures, aircraft, aerospace, automotive, recreational articles, and as adhesives.
Furthermore, the present invention relates to a curable material for use in electronic packaging applications wherein a thermoset material is required which has high fracture toughness and improved mechanical performance and is processable with existing manufacturing technology.
More particularly, this invention relates to a modified thermosetting material useful in the fabrication of printed circuit boards, semiconductor chip carriers, metal-core boards, reaction injection molded (RIM) cards, multichip modules, and multilayer thin film circuit structures, which may include more than one conductive layer and may incorporate electrical interconnections including through-holes or vias between two or more conductive layers or blind vias between two layers. This invention is well suited for use as a substrate material for surface mounted electronic components.
In addition, this invention relates to an improved material and printed circuit board made therefrom comprising a modified thermosetting material and reinforcement which exhibits high thermal stability, flame retardant characteristics and a controlled CTE.
2. Prior Art
Halogenated based thermosetting resins possess a number of attractive properties such as low dielectric constants, excellent thermal stability, low moisture uptake, high glass transition temperature, and good melt or solution processability characteristics.
Other attractive properties of these thermosetting resins include, methyl ethyl ketone (MEK) solubility, no volatile formation upon curing, outstanding adhesive properties, and photoimageability, (if desired).
However, use of these thermosetting materials in electronic packaging applications (e.g., prepregs, laminates, circuit boards) is limited due to their brittle nature which makes them susceptible to cracking when stressed or during processing such as via formation by, for example, drilling. This inherent brittleness is due to the high crosslink density of the networks which results in poor fracture toughness. Although there have been significant efforts to enhance the fracture toughness of the aforementioned thermosetting resins, further improvement in the mechanical properties of these materials is required in order to make them useful in electronic packaging applications. (As used herein, "fracture toughness" is a measure of how much energy is needed to propagate a crack in the plastic.)
U.S. Pat. No. 5,026,789 to Weber et al. and the publication by Weber et al., "Highly Damage Tolerant Carbon Fiber Epoxy Composites for Primary Aircraft Structural Applications", SAMPE Quarterly, 21(1), 46-51 (1989), describe the use of reactive poly(ether sulfone)s to enhance the toughness of epoxy resin thermosets. The structures of the epoxy resins and thermoplastic described in the patent are different from those in the present invention. The present invention describes halogenated materials which are MEK soluble/processable for electronic applications. Weber et al. do not discuss the incorporation of halogen-containing compounds to enhance compatibility/solubility characteristics.
U.S. Pat. Nos. 4,853,423, 4,975,319 and 5,096,771 all to Walles et al. describe a curable composition containing at least one bisphenol polyglycidyl ether, at least one epoxidized novolak and at least one brominated bisphenol in combination with polyphenylene ether. Thus these references also disclose a composition containing epoxy resin and a thermoplastic. The work by Walles et al. describes the incorporation of polyphenylene into brominated epoxy resins. The present invention describes the incorporation of a carefully designed halogenated poly(arylene ether) thermoplastic into thermosetting resins for improved mechanical properties. The system described by Walles et al. is not MEK processable and does not possess the enhanced mechanical properties as observed in the present invention.
U.S. Pat. Nos. 5,043,367, 5,073,605 and 5,108,842 all to Hallgren et al. describe a curable composition containing at least one bisphenol polyglycidyl ether, at least one epoxidized novolak and at least one brominated bisphenol in combination with polyphenylene ether. The work described by Hallgren et al. is analogous to that of Walles et al. noted above except that different catalysts/accelerators were evaluated. Hallgren et al. describe the incorporation of polyphenylene into brominated epoxy resins. The present invention describes the incorporation of a carefully designed halogenated poly(arylene ether) thermoplastic into thermosetting resins for improved mechanical properties. The system described by Hallgren et al. is not MEK prossessable and does not possess the enhanced mechanical properties as observed in the present invention.
U.S. Pat. Nos. 4,656,208, 4,822,832 and EP 0,193,082 to Chu et al. disclose the use of amine terminated poly(ether sulfone)s to enhance the toughness of epoxy resin thermosets. The structures of the epoxy resins and thermoplastic described in the patent are difference than those in the present invention. The present invention describes the incorporation of a carefully designed halogenated poly(arylene ether) thermoplastic into thermosetting resins for improved mechanical properties. The Chu et al. patent does not discuss the incorporation of halogen compounds to enhance compatibility/solubility characteristic.
J. E. McGrath et al., "Chemical Modification of Matrix Resin Networks with Engineering Thermoplastics", Polymer Bulletin, 13, 201-208 (1985) discloses the incorporation of hydroxyl terminated poly(ether sulfone)s to enhance the toughness of epoxy resin thermosets. The structures of the epoxy resins and thermoplastic described in the publication are different than those in the present invention. McGrath et al. describe the thermoplastic modification of simple diglycidyl ether of bisphenol A (DGEBA) based epoxy resins. The present invention describes halogenated poly(arlyene ether) thermoplastics which are MEK soluble/processable for electronic applications. McGrath et al. do not discuss the incorporation of halogen compounds to enhance compatibility/solubility characteristics.
G. R. Almen et al., "Semi-IPN Matrix Systems for Composite Aircraft Primary Structures", 33rd International SAMPE Symposium, Mar. 7-10, 1988, pp. 979-989, deals with the incorporation of a "polyaromatic thermoplastic" to improve the toughness of epoxy resin thermosets. The structures of the epoxy resins and thermoplastic described in the publication are different than those in the present invention. Almen et al. do not discuss the incorporation of halogen compounds to enhance compatibility/solubility characteristics.
As the prior art cited above discloses, poly(arylene ether)s have been repeatedly claimed in the prior art as modifiers for epoxy resins to enhance mechanical properties. However, after a review of the prior art with respect to the present invention, there are key distinctions not addressed by the prior art.